An LED (Light Emitting Diode) lighting has become widely used because the LED lighting is energy saving and has a longer operating life, and a number of lighting devices using the LED have been so far proposed. One of those lighting devices is a device in which a light reflector plate is arranged inside a frame of the lighting device and light is diffused and reflected to emit in order to improve an illuminance of the lighting device and to diffuse light.
For example, a certain reflector plate has been proposed that is inclined such that the reflector plate gets closer toward a light extraction portion as going farther from a light source (International Publication of PCT International Application No. WO2010-001604).
Also, a certain shape of a reflector plate has been proposed in which the reflector plate is formed in a curved shape for surface emitting (Japanese Patent Application Laid-Open Publication No. 2013-545662).
Yet also, as a method for extracting light, a certain method has been proposed in which a commonly-used diffusion sheet having a fine unevenness is stuck to an outer lens for extracting light (Japanese Patent Application Laid-Open Publication No. 2009-67098).
Yet also, a certain method has been proposed in which light from an LED light source is extracted after the light is multiply reflected in a light guide space having a curved shape (Japanese Patent Application Laid-Open Publication No. 2013-502042).
Yet also, a certain lighting device having a double layer structure has been proposed in which light sources are arranged in upper and lower two stages (Japanese Patent Application Laid-Open Publication No. Hei 11-185517).
However, the reflector plate disclosed in International Publication of PCT International Application No. WO2010-001604 is formed by laminating a PET film or white ink having light reflectivity on a metal or resin member, and therefore it is difficult to efficiently diffuse and reflect light.
According to Japanese Patent Application Laid-Open Publication No. 2013-545662, as the reflector plate is separately provided from a supporting structure such as a board or the like to which the LED light source is attached, and therefore the number of components increases and a configuration becomes complex.
The methods disclosed in Japanese Patent Application Laid-Open Publication No. 2009-67098 and Japanese Patent Application Laid-Open Publication No. 2013-502042 merely multiply reflect light from the LED light source by the diffusion sheet or the reflector plate and are not necessarily efficient. For example, when trying to extract uniformed light with a small number of LED light sources, it is required to provide a wider diffuse reflection area. Thus, in a case that an irradiation area is partitioned into a plurality of irradiation areas and light is to be extracted from the respective irradiation areas, it is required to provide a wider diffuse reflection area for each of the irradiation areas with respect to all irradiation areas. For this reason, the lighting device becomes enlarged.
In addition, as the lighting device is arranged inside an illumination space and thus a board of the lighting device adversely absorbs return light of the illumination light, which is emitted from the light source and then reflected by a reflecting surface, the use efficiency of the light is lowered. Also, as the LED board absorbs the light and is heated, it is concerned to shorten the operating life of the light source. Furthermore, as the LED is used as the light source and thus heat from the LED light source is transferred to a switch, a switch portion becomes heated so as to deteriorate the ease of use. Also, when used as an automotive interior illumination, it is in particular undesirable because the heat of the LED light source is radiated in an interior of the vehicle through the switch.
As a molded component of a highly reflective resin material such as a highly reflective polycarbonate or the like is used for a frame, the lighting device becomes heavy.
In Japanese Patent Application Laid-Open Publication No. Hei 11-185517, as the LED light sources are arranged in a staggered layout, it requires a number of LED light sources, and therefore the number of components increases and a configuration becomes complex.